1. Field of the Invention
The present invention relates to a method of producing Xanthan gum and, more particularly, to a method of producing Xanthan gum by culturing microorganisms in a specified culture medium.
2. Description of the Prior Art
Water-soluble viscous polysaccharides or gums include gum arabic, Xanthan gum, guar gum, and tragacanth gum. These gums are widely used in various industries including food, paint, paper making, and petroleum, and demand for such gums is increasing. Among these gums, Xanthan gum obtained by microorganic fermentation has excellent viscosity increasing effect, emulsification/stablization effect, particle/cell dispersion effect, and stabilizing effect against temperature changes, salts and pH. In view of these properties, the industrial application field of Xanthan gum as an effective additive is increasing.
Xanthan gum is conventionally produced by aerobic culture of a microorganism of genus Xanthomonas, e.g., Xanthomonas campestris, X. carotae or X. phaseoli in a culture medium consisting of a carbon source (e.g., glucose, sucrose, molasses, or starch), peptone, nitrogen, magnesium and trace amounts of other components. After culturing, the culture medium is sterilized, and Xanthan gum is allowed to precipitate by addition of an alcohol (e.g., ethanol or isopropyl alcohol). The precipitate is dried. Specific examples of microorganisms used in the production of Xanthan gum include X. campestris "NRRL B-1459" (Japanese Patent Disclosure No. 58-165798) and "ATCC 13951" (Japanese Patent Disclosure No. 58-146290).
However, Xanthan gum obtained by culturing conventional microorganisms of genus Xanthomonas using conventional culture media is significantly colored and must be bleached before industrial application. The bleaching process renders the culture process complex. In addition, this bleaching process must be intensive, thereby further complicating the culture process and increasing its cost.